Stopping flicker during updates

When making major changes to a list control (and other controls) it is a good idea to turn off updating of the control. To do this you would use SetRedraw(false) at the start of the change and SetRedraw(true) at the end, and then invalidate the control.

However, SetRedraw simply turns redraw on or off, it does not let you know whether or not redraw was on or off before the call. And there is no function that can tell you this.

For this reason, I have my own SetRedraw function that counts the number of times you have turned it on and turned it off.

Define a member variable:
     int m_redrawcount;

In your contructor do:

     m_redrawcount = 0;

And then define the following function (in this case for a list control):

void CMyListCtrl::SetRedraw( BOOL bRedraw) {
     if (! bRedraw) {
          if (m_redrawcount++ <= 0) {
               CListCtrl::SetRedraw(false);
          }
     } else {
          if (--m_redrawcount <= 0) {
               CListCtrl::SetRedraw(true);
               m_redrawcount = 0;
               Invalidate();
          }
     }
}

The first time you turn redraw off, the real SetRedraw function is called to turn redrawing off. Subsequently the function increases a counter when you requested redraw be turned off, and decreases it when you request redraw to be turned on again. When the counter gets back down to zero, the real SetRedraw function is called to turn redrawing back on again and the control is invalidated (so that redrawing actually takes place).

This means you can not put SetRedraw(false) at the start of, and SetRedraw(true) and the end of, any function that makes large changes to the lsit control (like loading, sorting, changing with column widths or order etc).



Comments

Leave a Comment
  • Your email address will not be published. All fields are required.

Top White Papers and Webcasts

  • Microsoft® Office 365 is a top choice for enterprises that want a cloud-based suite of productivity/ collaboration applications. With Office 365, you get access to Microsoft™ Office solutions practically anytime, anywhere, on virtually any device. It's a great option for current Microsoft users who can now build on their experience with Microsoft™ solutions while enjoying the flexibility of a cloud-based delivery. But even organizations with no previous investment in Microsoft will find that …

  • Salesforce has been recognized by Gartner as a leader in this report for three years in a row. This graphic was published by Gartner, Inc. as part of a larger research document and should be evaluated in the context of the entire document. The Gartner document is available upon request from Salesforce.com. Gartner does not endorse any vendor, product or service depicted in its research publications, and does not advise technology users to select only those vendors with the highest ratings. Gartner research …

Most Popular Programming Stories

More for Developers

RSS Feeds

Thanks for your registration, follow us on our social networks to keep up-to-date